A method of treating packaging materials to prevent discoloration

ABSTRACT

A method of treating packaging materials is disclosed wherein cartonboard or wrappers are treated with a boron-containing compound to prevent discoloration by the contents of the package.

United States Patent Meek, deceased [4 1 Mar. 21, 1972 54] METHOD OF TREATING PACKAGING MATERIALS TO References Cited 1721 memo Virgil Meek" deceased late 2,615,614 10/1952 Linda ..229/55 by Katherme Meek 3,000,751 9/1961 Davies et al..... ....117/152 x execumx 3,536,578 10/1970 Brundige et a1 ..117/152 X [73] Asslgneez :25 lgloicger & Gamble Company, Cmcm- FOREIGN PATENTS OR APPLICATIONS [22] Filed: Dec. 29, 1969 881,728 11/1961 Great Britain ..117/94 [21] App1.No.: 888,903 Primary ExaminerAlfred L. Leavitt Assistant Examiner-Edward G. Whitby Related pp Data Attorney-John V. Gorman and Stephen R. Smith [63] Continuation-impart of Ser. No. 734,197, June 4,

1968, abandoned. [571 ABSTRACT A method of treating packaging materials is disclosed wherein 52 us. Cl ..53/5, 117/152, 117/169, camnboard wmppm are treated with bommonmining 117/DIG 162/131 206/84 compound to prevent discoloration by the contents of the 51 1111. c1 ..D21h 5/22, D21h 1 10 package, [58] Field ofSearch ..l17/94,152,169,D1G. 10;

7 Claims, No Drawings A METHOD OF TREATING PACKAGING MATERIALS TO PREVENT DISCOLORATION CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 734,197, filed June 4, 1968, now abandoned.

FIELD OF THE INVENTION BACKGROUND OF THE INVENTION Some cartonboards very noticeably discolor or mottle when perborate-containing products are enclosed therein; for example, detergents containing sodium perborate have been found to cause such discoloration of sized and clay-coated solid bleached sulfate board. Perborates may appear in detergents in several forms. In one form (heat-fused perborate), sodium perborate tetrahydrate is fused with detergent crystalsat an elevated temperature in the range of 150 to 250 F. and the perborate-containing detergent crystals are rapidly cooled, such as by the process described in US. Pat. No. 2,876,200, Mar. 3, 1959 to Strain et al. In another form (dry mixed perborate), detergent granules are mechanically mixed with crystals which had been formed by agglomeratingparticles of a perborate such as sodium perborate tetrahydrate to achieve a perborate particle size sufficient to prevent segregation of the perborate and the detergent in the package. The composition resulting from addition of perborates to detergents typically comprises -30 percent by weight perborate (about 5 percent for heat-fused perborates, up to 30 percent for dry mixed perborates), the balance comprising amixture of an organic water-soluble detergent and a water-soluble alkaline builder in the ratio of detergent to'builder ranging from 5:1 to l :20. Typical detergents and builders are disclosed in U.S.Pat. No. 3,351,558, Nov. 7, 1967 to Roger E. Zimmerer at column 6, line 59 to column 9, line 75 and column 2, line 63 to column 3, line 38, respectively, the disclosure of the cited patent being herein incorporated by reference.

The discoloration problem can be avoided by using commercially available moisture barrier type cartons for packaging perborate-containing products. Both wax and polyethylene barriers in laminated cartons have proven effective. It is desirable, however, to avoid the added cost and special requirements of barrier cartons. Therefore, it 'is advantageous to provide a treatment for the cartonboard itself which will prevent mottling or discoloration, thereby eliminating the need for a barrier carton.

Similarly, pulpboard wrappers for bar soaps and bar soap outerwrappers containing paper frequently discolor when used with bar soaps containing perfumes and/or bactericides. Such discoloration can amount to yellowing of previously white materials or a substantial darkening of the material such as, for example, where a white packaging material turns brown. Whether or not all perfumed and/or bactericide-containing bar soaps can cause discoloration of these packaging materials is not known however, the propensity of a particular bar soap product to discolor can be determined by'observation on aging for several months or can-more rapidly be determined by overwrapping the packaged product with a material which is impermeable to the passage of gas therethrough and continuously subjecting the overwrapped packagedproduct to a temperature of about 150 F. for aperiod of about 2 weeks. Bar soap products which cause the pulpboard wrapper and/or the paper-containing outerwrapper to visually discolor during the foregoing 2 week test are the products which are hereinafter referred to as bar soaps.

Previous attemptsto prevent discoloration of the bar soap pulpboard wrappers and/or paper-containing outerwrappers included the use of dry wax sizing. This helped to some extent, but was expensiveand not completely effective. Another approach was to mask the item with opaque pigments; such, for example, as loading an outerwrapper with titanium dioxide or printing with white ink on the exterior surface of the outerwrapper. These approaches were expensive since the former required the use of substantially more pigment than was normally used with a high quality wrapper and the latter required an additional printing operation.

It was discovered that if the above-described materials are treated with a boron-containing compound, for example, sodium metaborate, at a level within the range of from aboutp.p.m. to about 850 p.p.m. of boron by weight of finished material discoloration is inhibited. The exact mechanism of the discoloration and/or the inhibition is not known; however,

it is theorized that discoloration is caused by the contents of the package (i.e., the perborate of the perborate-containing product or the perfume and/or the bactericide of the bar soap) reacting in some way with the cellulose molecules of the untreated packaging materials-for example, by oxidation or the formation of organic condensation products. The discoloration is believed inhibited by the present invention because the boron reacts with the reactive groups of the cellulose molecules (such as the carbonyl, carboxyl and hydroxy groups) to form complexes which do not change color and which tie up the groups and prevent the above-described reactions which cause discoloration.

Boron-containing compounds have previously been used as fungistatic or fungicidal agents in cartonboard. Representative of such use of compounds such as sodium metaborate and sodium pentaborate is the disclosure in British Pat. No. 881,728. This patent teaches that borate is an effective fungicidal agent when incorporated in concentrations of 6 percent borate calculated as B 0 by weight of water in the aqueous phase of the product, and which aqueous phase has a pH ofat least 5.2.

Though 'the patent cited above teaches incorporation of boron-containing compounds in paper or cartonboard, it does not teach the range of boron content of the present invention, nor the specific discovery and use of this invention, nor does it suggest the same in the environmental conditions conducive to the discoloration problem. As a matter of fact, the prior art simply discloses that boromcontaining compounds are only a few of a multitude of agents adapted to be incorporated in paper or cartonboard for microbiological purposes.

OBJECTS OF THE INVENTION It is therefore an object of this invention to provide a method of packaging products in which the paper or board has been treated to inhibit discoloration normally experienced in such packages.

A further object of this invention is to provide a package enclosing a perborate-containing product, which package is not subject to such discoloration.

A still further object of this invention is to provide a package enclosing a perfume and/or bactericide-containing bar soap product, which package is not subject so such discoloration.

SUMMARY OF THE INVENTION Briefly stated in accordance with one aspect of the present invention, packaging materials susceptible to discoloration are treated with a boron-containing product selected from the group consisting of borax, boric acid, sodium metaborate and mixtures thereof, said treatment causing boron to be added to such material inquantities of at least about 80 parts by weight of boron per million parts of finished packaging material.

In accordance with another aspect of the present invention there is provided a package comprising a carton in which the cartonboard has been treated as described above and a perborate-containing product contained in said package in direct contact with the interior surface thereof.

in accordance with still another aspect of the present invention there is provided a package for a bar soap product in which the packaging material contains boron in the aforesaid range.

DESCRIPTION OF THE PREFERRED EMBODIMENTS l. CARTONS FOR PERBORATE-CONTAINING PRODUCTS Commercial practice of the invention can embody any of several methods of treating the cartonboard. One such method is to add a solution of the boron compound to the carbonboard medium at a station on the papermaking machine, as by using a drum coater, size press, or water box on the board machine. A second method of treating the cartonboard comprises adding the boron solution to the materials normally used for coating or sizing cartonboard (such as clay or starch) and applying the coating or sizing mixture to the cartonboard by the usual methods employed in the papermaking art. A third method is to use a printing press or coating equipment for applying the boron solution to the finished cartonboard. This can be an independent operation or can be done in connection with the carton printing or converting operation. A further method which is applicable to white lined cylinder boards, such as white patent-coated newsboard and similar cartonboards, (those boards can be generally described as comprising a relatively thick layer of inexpensive pulp, such as from waste paper, and a relatively thin layer of white or bleached pulp at one or both surfaces), is addition of the inhibitor to the aqueous mixture which is laid down to form the top white liner of the cartonboard. Each of the methods cited involves only the use of equipment and techniques well known in the carton manufacturing art and needs no further exposition here.

After the cartonboard has been treated as described above, it is converted into cartons by ordinary carton manufacturing methods, such as printing and die cutting carton blanks and gluing and folding the blanks (by hand or machine) to form the carton structure. The addition of boron to the cartonboard in no way limits the usual methods of carton manufacture.

Filling the cartons with perborate-containing products, such as certain detergents, is also within the capabilities of one or ordinary skill in the packaging arts and presents no unusual problems. The filling may be readily accomplished by any of a number of techniques employing manual operations or automatic or semiautomatic machines.

Several boron-containing compounds result in effective in-' hibition of cartonboard mottling in perborate-containing product packages. For example, sodium metaborate, boric acid, and borax have all been tested and found effective, as have mixtures of borax and boric acid and other mixtures of the materials. Sodium metaborate appears to be somewhat more effective at lower concentration levels, however.

The mottling effect is independent of the pH of the particular inhibitor solution applied, and the minimum concentration of boron imparted by borax, sodium metaborate, boric acid, or mixtures thereof to cartonboard required to acceptably inhibit mottling is about 80 parts by weight boron per million parts finished cartonboard (p.p.m. boron) applied to the surface desired to be treated. Such treatment causes the material in the region of the surface, i.e., that comprising the surface and that directly underlying it, to be exposed to the boron. Thus, the cellulosic materials visible to an observer are treated to inhibit discoloration, whereas such materials sufficiently spaced from the surface (for example, interior portions, thickness-wise, of the cartonboard) do not have to be treated. Inhibitor concentrations substantially higher than the above have also proved effective, but quantities greater than about 850 p.p.m. boron are preferably not used because the same is unnecessary and therefore uneconomical and because borates, when used in large quantities, can cause problems of agglomeration and precipitation of coating materials. The p.p.m. boron can, however, be increased as needed to satisfactorily inhibit mottle with products of higher mottling potential. The amount of increase in p.p.m. boron required within the desired range in such an instance can be determined by the method of specified in Example V.

From the standpoint of economy and convenience it is preferable to apply the boron-containing compound to the surfaces the cartonboard for which protection is desired, and more particularly to the outside surface of the cartonboard if only one surface is to be so treated. Mottle resistance of the outside surfaces of cartons which had been treated on the inside surface only is, generally speaking, commercially unacceptable, though someimottle inhibiting effect can be observed if higher concentrations of inhibitor solution are so-applied. The location of the boron-containing compound depends upon the type of cartonboard used in a package. For example, an all white board such as solid bleached sulfate board, should preferably be treated on both sides as some product formulas tend to produce unsightly discoloration both inside and outside a carton manufactured from all white solid bleached cartonboard. White patent-coated newsback, chip or Kraft-backed cartonboards, however, require treatment only on their outside white surfaces, since the inside surface is of such color as to mask any discoloration on that surface.

The examples set forth below illustrate the limitations and preferences described above and claimed at the end of this specification. In the results tabulated with the examples, the term mottle inhibited indicates that careful inspection of the sample revealed no mottling thereof, the term slight trace indicates that upon careful scrutiny a small mottling effect was observed, the term trace indicates that casual inspection reveals a light mottling effect, the term bad in dicates that a severe mottling effect was observed, and the term noticeable indicates that a mottling effect intermediate that termed trace and that termed bad was observed. Mottling termed slight trace" or mottle-inhibited" is considered commercially acceptable inasmuch as neither effect would be objectionable to the consumer. In the examples, tabulation of commercially unacceptable results is provided for comparison with those treatments which produced commercially acceptable results.

Examples I-IV are not quantitative, but are included to demonstrate effectiveness of the boron treatment using various boron-containing compounds and boron-containing solutions having various pH values. In examples l-IV no attempt was made to control the amount of solution applied to the cartonboard tested; hence, the results obtained with a given solution strength in Examples I-IV do not necessarily correspond to the results obtained with the same solution strength in Example V wherein boron content was accurately detennined.

In each of the examples, the cartonboard tested is recited as having been sized on both sides and clay-coated on one side. The sizing and coating compounds were representative of those which are typically commercially available, and the specific compositions of the compounds used have no substantial effect on the results.

The mottle inhibiting compound (contained in an aqueous solution) in each example was applied to the cartonboard with an eyedropper. The solution was then drawn down across the board surface with a glass rod to evenly and completely wet the surface.

The term commercially identical is used in some of the examples below. The term refers to cartonboard made by the same process and having the same composition as its antecedent within commercial manufacturing tolerances.

EXAMPLE I Four solid bleached sulfate cartons which had been sized on both sides and clay-coated on the outside were treated respectively with 10 percent aqueous solutions of boric acid having a pH of 3.8, borax having a pH of 9.1, a boric acid/borax mixture having a pH of 7.0 and sodium metaborate having a pH of l 1.2. The solutions were applied to the inside surfaces of the cartonboard samples with a glass rod, and the cartons were filled with a granular detergent composition comprising about 5 percent by weight heat-fused perborate, about 47 percent sodium tripolyphosphate builder, and about 16 percent detergent (45 parts linear alkylbenzene sulfonate to 55 parts tallow alkyl sulfate), individually foil overwrapped, and stored at 140 F. for two weeks. Evaluation of the samples revealed that irrespective of pH values, each of the tested treatments successfully inhibited mottling of the treated surfaces by the per borate.

EXAMPLE II Panels of solid bleached sulfate cartonboard were prepared by applying inhibitor solutions to approximately half of one surface on each panel and applying clay coatings over the entire panel on the said one surface. Three groups of three samples each were prepared. The three groups were treated with solutions containing borax, boric acid and sodium metaborate, respectively, and the samples within the groups were treated with aqueous inhibitor solutions having concentrations of l, 5 and percent, respectively. The treated samples were then inserted as panels in detergent cartons, the treated side of the panels being placed to the outside of the cartons. The thusly prepared cartons were filled with the detergent described in Example I (containing 5 percent by weight heat-fused sodium perborate foil overwrapped and stored for two weeks at 140 F. After the storage period, untreated areas of the cartons were badly mottled, and evaluation of the treated areas yielded the mottling results tabulated below.

Substantially similar results are achieved when white patent-coated newsback, chip-backed and Kraft-backed cartonboards are substituted for the solid bleached sulfate cartonboard of this example.

EXAMPLE III Cartonboard panels which were commercially identical to those of Example II were prepared in three groups of three each and incorporated in detergent cartons as described in Example II and the cartons were filled with a detergent composition comprising about 10 percent by weight dry mixed sodium perborate, about 30 percent sodium tripolyphosphate builder, and about 28 percent alkyl benzene sulfonate detergent, foil overwrapped, and stored for two weeks at 120 F. At the end of the storage period, untreated areas of the cartons were unacceptably mottled, and evaluation of the treated areas yielded the results tabulated below.

inhibited inhi ited inhibited EXAMPLE IV Cartonboard panels which were commercially identical to those of Example II were prepared by applying inhibitor solutions to approximately half of one surface on each panel and applying clay coatings over the entire panel on the said one surface and by applying inhibitor solutions to approximately one-half of the other surface corresponding to the treated portion of the said one surface. Three groups of three samples each were prepared. The three groups were treated with solutions containing borax, boric acid, and sodium metaborate, respectively, and the samples within the groups were treated with aqueous inhibitor solutions having concentrations of l, 5 and 10 percent, respectively. The treated samples were then inserted as panels in detergent cartons, the clay-coated side of the panels being placed on the outside of the cartons. The thusly prepared cartons were filled with the granular detergent described in Example I (containing 5 percent by weight heatfused perborate), foil overwrapped, and stored for two weeks at F. After the storage period, untreated areas of the cartons were badly mottled, and evaluation of the treated areas yielded the results tabulated below.

Three groups of twelve panels each of sized solid bleached sulfate cartonboard were prepared for testing to determine the minimum amount of boron content required for effective mottle inhibition. Each of the panels in the first group was treated on one surface with one of four sodium metaborate solutions and clay-coated on the other surface, each of the panels in the second group was treated on one surface with one of four aqueous solutions of sodium metaborate and clay-coated over the treatment, and each of the panels in the third group was treated on both its surfaces with one of four sodium metaborate solutions and clay-coated on one of its surfaces.

The groups of 12 panels were subdivided into four sets of three panels. Each of the three panels in the first set was treated with an aqueous solution containing 0.5 percent by weight sodium metaborate; each of the panels in the second set was treated with a 1.0 percent sodium metaborate solution; each of the panels in the third set was treated with a 2.5 percent sodium metaborate solution, and each of the panels in the fourth set was treated with a 5.0 percent sodium metaborate solution. The solutions were applied by drawing them down over the surfaces with a glass rod, and each of three panels within a set received insofar as practical, quantitatively identical treatments. All panels were weighed before and after the sodium metaborate treatment to enable calculation of the boron added to each panel, and one panel with each of the different solution strengths was taken from each of the three groups and submitted to a laboratory for analysis of boron content.

After panel preparation, two panels from each set of three were inserted in detergent cartons as replacements for the ordinary detergent carton panels, the cartons were filled with the granular detergent described in Example I (containing 5 percent by weight heat-fused perborate), foil overwrapped, and stored at 140 F. for two weeks.

The amount of boron added to each panel was calculated by multiplying the weight gained by the panel upon treatment with the sodium metaborate solution by the ratio of the atomic weight of boron to the molecular weight of sodium metaborate and then multiplying the resulting product by the percentage by weight of sodium metaborate in solution.

The analysis of panels for boron content involved ashing samples from the panels, obtaining an extract, and analyzing the extract for boron content by the classical carmine procedure, which is described in Hatcher and Wilcox, Colorimetric Determination of Boron Using Carmine, 22 Analytical Chemistry 567 Apr. 1950).

The extraction was accomplished in the following manner. 3 to 5 gram samples of the coated panels were cut from various areas of the panel being tested and placed in platinum crucibles and allowed to char thoroughly on a hot plate at full heat. The crucibles were then placed in a furnace at 300400 C., the furnace temperature was gradually increased to 550575 C. and maintained there for 45-60 minutes. The samples were allowed to cool and then' transferred to stainless steel breakers, using a 0.1 percent solution of sodium carbonate to complete the transfer. Sodium carbonate solution (0.1 percent) was added to the beakers to provide a total 'volume of about 50 ml. and the solution was boiled for 20 minutes. The solution was then filtered by decantation through a 0.45 micron filter, and the filtrate was collected in a polypropylene container. The ash extration was repeated on the resulting precipitate with 25 ml. of the sodium carbonate solution, the solution was filtered, and a minimum amount of hot water was used to complete the transfer from the beaker to the filter and wash the precipitate in the filter. The filtrate was then submitted to analysis for boron by the classical carmine procedure.

Visual evaluation of the outer surfaces of the test panels of the sample cartons previously described, calculation of estimated boron content of each sample, and analysis of panels for actual boron content yielded the results tabulated below:

Total.

Several panels which had been treated on their outside sur-' face only had a brownish discoloration on their inside surfaces. This inside discoloration was not present on the panels which had been treated on the inside only or on both surfaces.

Substantially similar results are also obtained in Example V when the following substitutions are made.

i. Non-sized and uncoated solid bleached sulfate cartonboard is substituted for the sized cartonboard of Example V.

2. The boron-containing compound is added to a standard commercially available sizing or coating material and the thusly prepared sizing or coating material is applied to one or both (as the case may be) surfaces of the cartonboard in quantities sufficient to result in corresponding depositions of boron in substitution for the step of Example V wherein aqueous solutions of sodium metaborate were drawn over the surfaces with a glass rod.

in each of Examples l-V above, substantially similar results are obtained when boric acid is substituted for the particular inhibitor specified and ethyl alcohol is substituted for water as a solvent for the boron-containing compound.

Substantially similar results are obtained in Example V when borax, boric acid and mixtures of two or all of the group consisting of borax, boric acid and sodium metaborate are substituted for sodium metaborate in quantities sufficient to result in corresponding depositions of boron (i.e., similar values of p.p.m. boron). It is noted that the solid bleached sulfate cartonboard which is commercially acceptable with respect to mottle resistance when treated on the outside surface only contains between about 60 and about 180 p.p.m.

boron (the results for an outside treated sample at 59 p.p.m. boron level indicate that mottling was Noticeable, and results for an outside treated sample at a 182 p.p.m. boron level indicate that mottling was inhibited.) A level of p.p.m. boron when applied to the outside surface only is considered sufficient to yield commercially acceptable results, i.e., no more than a slight trace of mottling would appear on the outer surface. When both surfaces are treated with inhibitor (for example, if it is important that the inner and outer surfaces not be discolored), commercially acceptable results are obtained with between about and 300 p.p.m. boron total (i.e., between about 65 and p.p.m. boron applied to each surface). A level of 80 p.p.m. boron applied to each side is also considered sufficient for commercially acceptable results, i.e., no more than a slight trace" of mottling would appear on either surface.

Substantially similar results are also obtained in Example V where white patent-coated newsboard and similar lined cylinder boards are substituted for sized solid bleached sulfate board.

Substantially similar results are also obtained in Example V when, instead of applying the inhibitor as recited therein, the boron-containing compound is applied to white lined cylinder boards by adding it to the aqueous mixture which is laid down to form the top white liner of the cartonboard.

ll. PACKAGING MATERIALS FOR BAR SOAPS With respect to treatment of packaging materials which are normally discolored by a perfumed and/or bactericide-containing bar soap, the same general methods can be used which were taught in connection with treatment of cartonboard for perborate-containing products. A solution of the boron compound can be added to such materials at a station on the papermaking machine; the boron solution can be added to coating materials, if used, and the coating applied in the normal manner; the boron solution can be applied individually by a printing or coating operation; or the boron solution can be added directly to the beater so that the material is distributed throughout the sheet when formed. Following treatment, the packaging materials are employed in the normal manner in forming an enveloping enclosure about perfumed and/or bactericide-containing bar soaps which have the propensity to discolor cellulosic packaging materials. As used herein, the term bar soap includes detergent bar forms of products made from soap, from non-soap detergents and from mixtures thereof. The prior art is replete with suitable examples of such materials and so further exposition thereof is unnecessary. The methods and equipment for forming such packages are also well known in the art and therefore not described herein.

The types of boron-containing compounds which are effective, along with the quantity range, i.e., about 80 to about 850 p.p.m. boron, and with other remarks relating to pH and other general aspects of the treatment described above respecting cartonboard for perborate-containing products are also applicable to the treatment of the bar soap packaging materials. However, it has been found that while treatment of bar soap wrapping materials in the low end of the range is effective in inhibiting a great deal of discoloration, it is preferable that such treatment be in the 600 to 850 p.p.m. range to be certain of commercially acceptable results.

Although the treatment of the present invention is useful in treating all sorts of paperboard and paper packaging materials subject to the discoloring effects of perfumed and/or bactericide-containing bar soaps, it is particularly useful in connection with such packaging materials which are also treated with a branched chain sodium dodecyl benzene sulfonate (ABS). The ABS is a fungistatic/fungicidal agent and can be present in quantities upwards of about 7,000 parts by weight per million parts finished material for effective mold growth inhibition for a substantial period of time. ABS in the material aggravates the discoloration problem, possibly by acting as a catalytic agent or in some other way promoting the reactions which cause the packaging materials to change color, in the absence of the subject discoloration-inhibiting treatment. It is not essential, however, that the ABS be present in as great a quantity as that required to assure inhibition of mold growth for the ABS to perform its discolor-aggravating function since quantities of 1,000 p.p.m. ABS, perhaps even less, are sufficient to so-function. In any event, the present invention has particular utility in protecting ABS-treated packaging materials because of their high susceptibility to discoloration.

The examples set forth below are tabulated using terms similar to those previously described. Thus, the results, in increasing order of discoloration are: discoloration inhibited, slight trace, trace, noticeable and bad. In each of the examples, the pulpboard wrapper is 0.009 inch thick fully bleached sulfate board containing ABS in quantities ranging from about 6,300 to about 10,000 parts ABS per million parts finished board. The outerwrapper is 45 pound per ream (24 in. X 36 in. 500) fully bleached sulfate/sulfite soap wrapper paper.

The amount of boron added to the treated packaging material was calculated by multiplying the weight gained upon treatment, by the ratio of the weight of boron to the molecular weight of the boron compound used and then multiplying the resulting product by the percentage by weight of the boron compound in solution.

EXAMPLE VI A perfumed, bactericide-containing bar soap product sold commercially was found to cause bad discoloration, i.e., darkening of both pulpboard wrapper and the paper-containing outerwrapper upon aging. Four bars of soap which were commercially identical with the bar soaps found to so-discolor the packaging materials were produced. Four pulpboard blanks were cut lengthwise in half and the half of each to be treated was weighed. Then the weighed halves were each individually treated with a boron-containing solution and weighed immediately. The treatment was accomplished by applying a 17 percent by weight aqueous solution of sodium metaborate to one surface of each half treated by means of a gravure hand proofer, using a 150 line screen. Following air drying the halves of each pulpboard blank were reassembled by using transparent pressure sensitive tapes to reunite the halves. Then each blank was wrapped about a bar of soap with the treated surface of the treated half facing inwardly and the wrapper secured in that condition by another piece of transparent tape. Next, each wrapper bar was overwrapped in a sheet of aluminum foil and stored for two weeks in an oven maintained at 150 F. After the storage period, the inwardly facing surface was evaluated for discoloration with the results tabulated:

Substantially similar results are achieved when the treated halves are provided with the same amounts of boron by treatments with solutions of borax, boric acid and mixtures of borax and sodium metaborate; borax and boric acid; borax, sodium metaborate and boric acid; and boric acid and sodium metaborate.

Substantially similar results are also achieved when modified bar soaps, which are identical in composition with that tested above with the exception that the perfume has been omitted, are substituted in the test bars, and when outerwrappers are also similarly cut, treated, assembled and applied over the pulpboard wrapper before overwrapping with foil and storing for 2 weeks at F.

EXAMPLE VII A perfumed bar soap product sold commercially is found to cause bad discoloration, darkening, of its pulpboard wrapped and its outerwrapper upon aging. Four bars of soap which are commercially identical with the bar soaps found to so-discolor the packaging materials are produced, along with four bars which are also identical in composition, with the exception of the omission of the perfume therefrom. Pulpboard wrappers containing about 6,300 p.p.m. ABS per million parts of finished board are then cut, halves thereof treated, reassembled, wrapped about the bar soaps, overwrapped with foil and stored for 2 weeks at 150 F. as set forth in Example VI. At the end of the storage period the inwardly facing surfaces of the wrappers are evaluated for discoloration as tabulated below:

Bar soap Calculated -ldenti Halt" Amount Discoloration fication Evaluated of Boron Evaluation Perfumed:

l Treated 700 p.p.m. Inhibited l Untreated 0 Bad 2 Treated 625 p.p.m. Inhibited 2 Untreated 0 Bad 3 Treated 750 p.p.m. Inhibited 3 Untreated 0 Bad 4 Treated 825 p.p.m. Inhibited 4 Untreated 0 Bad Bar Soap Calculated Identi- Half Evaluated Amount Discolotation fication Evaluated of Boron Evaluation Unperl'umed:

l Treated 850 p.p.m. Inhibited I Untreated 0 Slight trace 2 Treated 800 p.p.m. Inhibited Z Untreated 0 Slight trace 3 Treated 700 p.p.m. Inhibited 3 Untreated 0 Slight trace 4 Treated 750 p.p.m. Inhibited 4 Untreated 0 Slight trace Substantially similar results are achieved when the treated halves are provided with the same amounts of boron by treatments with solutions of borax, boric acid and mixtures of borax and sodium metaborate; borax and boric acid; borax, sodium metaborate and boric acid; and boric acid and sodium metaborate.

Substantially similar results are also achieved when pulpboard blanks containing ABS in quantities of 1,000; 7,000; 8,000; 9,000 and 10,000 parts by weight per million parts furnished board are substituted for the above-used pulpboard.

EXAMPLE VIII The tests involving the perfumed bars of Example VII are repeated with the exception that bar soap outerwrappers are also cut in half, treated and assembled in the manner of the pulpboard wrapper and wrapped over the pulpboard wrapper with the treated side facing inwardly prior to the foil overwrapping. The results are:

Bar soap Calculated Identi- Half Amount Discoloration fication Evaluated of Boron Evaluation l Pulpboard 850 p.p.m. Inhibited treated I Pulpboard Bad untreated l Outerwrapper 700 ppm. Inhibited treated I Outerwrapper 0 Bad untreated 2 Pulpboard 825 p.p.m. Inhibited treated 2 Pulpboard 0 Bad untreated 2 Outerwrapper 650 p.p.m. Inhibited treated 2 Outerwrapper 0 Bad untreated 3 Pulpboard 675 p.p.m. Inhibited treated 3 Pulpboard 0 Bad untreated 3 Outerwrapper 600 ppm. Slight trace treated 3 Outerwrapper 0 Bad untreated 4 Pulpboard 1525 ppm. Slight trace treated 4 Pulpboard 0 Bad untreated 4 Outerwrapper 775 p.p.m. Inhibited treated 4 Outerwrapper 0 Bad untreated Many modifications of the above invention may be used and it is not intended to hereby limit it to the particular examples described. The terms used in describing the invention are used in their descriptive sense and not as terms of limitation, it being intended that all equivalents thereof be included within the scope of the appended claims.

What is claimed is:

l. A method of inhibiting discoloration of a surface of a packaging material, said surface discoloration being nonnally caused by a reaction with product contents selected from the group consisting of perborate-containing products, perfumed bar soaps, bactericide-containing bar soaps and perfumed bactericide-containing bar soaps, said method comprising the steps of:

A. treating said packaging material at least in the region of said surface with a boron-containing product selected from the group consisting of borax, boric acid, sodium metaborate and mixtures thereof, said treatment imparting about to about 850 parts by weight boron per million parts finished packaging material, and

B. forming said treated packaging material into an enclosure about said product contents.

2. The method recited in claim 1 wherein said treatment comprises adding said boron-containing compound to the material for sizing said packaging materials and applying said sizing material to the said surface of said packaging material.

3. The method recited in claim 1 wherein said treatment comprises adding said boron-containing compound to the coating materials used for said packaging material and applying said coating materials to the said surface of the packaging material.

4. The method recited in claim 1 wherein said treatment with a boron-containing compound comprises applying a solution thereof to said surface of said packaging material.

5. The method recited in claim 1 wherein said packaging material is solid bleached sulfate cartonboard.

6. The method recited in claim 1 wherein said packaging material is a white line d c linder board.

7. The method recite in claim 6 wherein said treatment comprises adding said boron-containing compound to the aqueous mixture which is laid down to form the top white liner of the white lined cartonboard. 

2. The method recited in claim 1 wherein said treatment comprises adding said boron-containing compound to the material for sizing said packaging materials and applying said sizing material to the said surface of said packaging material.
 3. The method recited in claim 1 wherein said treatment comprises adding said boron-containing compound to the coating materials used for said packaging material and applying said coating materials to the said surface of the packaging material.
 4. The method recited in claim 1 wherein said treatment with a boron-containing compound comprises applying a solution thereof to said surface of said packaging material.
 5. The method recited in claim 1 wherein said packaging material is solid bleached sulfate cartonboard.
 6. The method recited in claim 1 wherein said packaging material is a white lined cylinder board.
 7. The method recited in claim 6 wherein said treatment comprises adding said boron-containing compound to the aqueous mixture which is laid down to form the top white liner of the white lined cartonboard. 